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Publication numberUS6624086 B1
Publication typeGrant
Application numberUS 09/640,250
Publication dateSep 23, 2003
Filing dateAug 16, 2000
Priority dateSep 15, 1999
Fee statusPaid
Also published asUS7153782, US20040018730
Publication number09640250, 640250, US 6624086 B1, US 6624086B1, US-B1-6624086, US6624086 B1, US6624086B1
InventorsMona M. Eissa
Original AssigneeTexas Instruments Incorporated
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Effective solution and process to wet-etch metal-alloy films in semiconductor processing
US 6624086 B1
Abstract
A solution and method is described for etching TaN, TiN, Cu, FSG, TEOS, and SiN on a silicon substrate in silicon device processing. The solution is formed by combining HF at 49% concentration with H2O2 at 29%-30% concentration in deionized water.
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Claims(7)
I claim:
1. A solution for etching TaN during semiconductor device processing, consisting essentially of combining HF with a concentration of 49% with H2O2 with a concentration of 29%-30% in deionized water wherein said solution has a volume ratio greater than 1:1:20 of HF:H2O2:deionized water.
2. A solution for etching TaN during semiconductor device processing, consisting essentially of combining HF with a concentration of 49% with H2O2 with a concentration of 29%-30% in deionized water wherein said solution has a volume ratio of 2:1:21 of HF:H2O2:deionized water.
3. A solution for etching TaN during semiconductor device processing, consisting essentially of combining HF with a concentration of 49% with H2O2 with a concentration of 29%-30% in deionized water wherein said solution has a volume ratio of 3:2:10 of HF:H2O2:deionized water.
4. A solution for etching TaN during semiconductor device processing, consisting essentially of combining HF with a concentration of 49% with H2O2 with a concentration of 29%-30% in deionized water wherein said solution has a volume ratio of 3:1:10 of HF:H2O2:deionized water.
5. A solution for etching TaN, TiN, Cu, FSG, TEOS, and SiN in silicon device processing, consisting essentially of combining HF with a concentration of 49% with H2O2 with a concentration of 29%-30% in deionized water from 40 C. to 50 C. wherein said solution has a volume ratio of 2:1:21 of HF:H2O2:deionized water.
6. A solution for etching TaN, TiN, Cu, FSG, TEOS, and SiN in silicon device processing, consisting essentially of combining HF with a concentration of 49% with H2O2 with a concentration of 29%-30% in deionized water from 40 C. to 50 C. wherein said solution has a volume ratio of 3:2:10 of HF:H2O2:deionized water.
7. A solution for etching TaN, TiN, Cu, FSG, TEOS, and SiN in silicon device processing, consisting essentially of combining HF with a concentration of 49% with H2O2 with a concentration of 29%-30% in deionized water from 40 C. to 50 C. wherein said solution has a volume ratio of 3:1:10 of HF:H2O2:deionized water.
Description

This application claims priority under 35 USC 119(e)(1) of provisional application No. 60/154,082 filed Sep. 15, 1999.

FIELD OF THE INVENTION

The present invention relates to a wet chemical etch process for etching fluorinated silicon oxide, TEOS, TiN, TaN, SiN, and copper films in semiconductor processing without damaging the silicon substrate surface. The wet chemical etching process leaves the silicon surface hydrophilic. The process uses a mixture of H2O2 and HF in de-ionized water.

BACKGROUND OF THE INVENTION

In the fabrication of an integrated circuit on a silicon substrate a number of metal alloy layers are formed. Titanium nitride (TiN) films are used as barrier layers for aluminum metal lines. These barriers layers are necessary to prevent the unwanted chemical interaction of the aluminum metal lines with other layers in the circuit. Currently, hot concentrated sulfuric acid and hydrogen peroxide or a hot SC2 (HCl+H2O2+DIW) solution is used to wet etch TiN films. Both of these solutions will attach the Silicon substrate leading to a roughening of the surface or the creation of voids. With the advent of the use of copper metal lines, tantalum nitride (TaN) films are finding increasing use as barrier layers for copper films. These TaN films often act as diffusion barriers preventing the diffusion of copper from the metal lines into other parts of the circuit where it would inhibit proper circuit operation. There is not a suitable wet etch process for removing TaN films from a silicon substrate. In addition, it is often necessary to etch these copper film in the presence of a patterned photoresist. Copper can be etched using a hot concentrated sulfuric acid or a hot SC2 (HCl+H2O2+DIW) solution. These solutions will attack the photoresist films in current use and therefore cannot be used in the presence of photoresist films. Silicon nitride (SiN) films are used extensively in the fabrication of integrated circuits both as part of the transistor structure and as a barrier layer or liner layers. Current techniques to remove SiN involve the use of phosphoric acid at temperatures as high as 160 C. As in the case of hot sulfuric acid, hot phosphoric acid will attack the silicon substrate. Fluorinated silicon dioxide (FSG) and TEOS are typically etched using HF solutions which can in some instances attack the silicon substrate. In each instance of the above discussed materials/metal-alloys it will be necessary to remove these layers from the silicon substrate without producing damage to the surface. This need might arise during the reworking of a silicon wafer through a particular processing sequence involving one of the above mentioned films. Reworking of a silicon wafer through a processing sequence is often necessary due to mis-processing of the wafer during the sequence. A need therefore exists for a wet chemical process that effectively and completely removes TaN, TiN, SiN, Cu, FSG, and TEOS from the surface of a silicon substrate without damaging said surface.

SUMMARY OF INVENTION

The instant invention is a process to wet-etch TaN, TiN, SiN, Cu, FSG, and/or TEOS films. Solutions of hydrofluoric acid (HF) and hydrogen peroxide (H2O2) are used for the wet etch. De-ionized water is used to dilute all the solutions used and will be represented by the symbol DIW. In all solutions of the instant invention, the presence of H2O2 in the solution will leave the silicon substrate surface hydrophillic. This will reduce the number of particles left on the surface after the chemical process. In addition, the solutions described will not attack photoresist. This allows the above mentioned films to be etched in the presence of patterned photoresist.

The HF:H2O2:DIW solution provides a wet chemical process to remove TaN without damaging the silicon substrate. In addition it will not attack photoresist and therefore can be used in a process involving patterned photoresist. In addition, the solution will etch SiN, TiN, FSG, TEOS and Cu either singly or simultaneous along with TaN without damaging the silicon substrate.

DETAILED DESCRIPTION OF THE INVENTION

It is often necessary to remove TiN, TaN, SiN, Cu, FSG and/or TEOS from a silicon substrate without damaging the surface of said substrate. The instant invention describes a wet chemical etch method for the removal of such films from a silicon substrate. For all the chemical solution examples described herein, it should be assumed that the hydroflouric acid (HF) used has a 49% concentration (24.5 moles/L) and the hydrogen peroxide (H2O2) used has a 29%-30% concentration (8.8 moles/L). In an embodiment of the instant invention, HF with a concentration of 49% and H2O2 with a concentration of 29%-30% is mixed together and diluted in deionized water to specific volume rations for etching TaN, TiN, SiN, Cu, TEOS, and FSG. TEOS is used to represent silicon oxide formed by the pyrolysis of the alkoxy compound tetraethoxysilane.

An embodiment of the wet chemical etch solution is a volume ratio of 2:1:21 of HF:H2O2:DIW. For most applications in the processing of semiconductor integrated circuits, this volume ratio will result in reasonable etch rates for TaN. In addition to etching TaN without damaging the silicon substrate, the 2:1:21 solution will simultaneously etch all the above compounds with a selectivity of FSG>TEOS>CU>SiN>TiN>TaN. Changing the volume ratios of HF and H2O2 will affect the etch rate of each material but the overall trend in etch rate selectivity will remain unchanged. It should be noted that the 2:1:21 (HF:H2O2:DIW) solution is effective at room temperature and should be used at such. It can however be used at temperatures greater than room temperature. This solution and all solutions described in the instant invention can be used by immersing the silicon substrate in the solution as part of a batch type process or by spraying the solution unto the surface of each wafer.

Another embodiment of the wet chemical etch solution is a volume ratio of 3:2:10 of HF:H2O2:DIW and a third embodiment is a volume ratio of 3:1:10 of HF:H2O2:DIW. In general, the more concentrated the solution the faster the reaction rate.

For the etching of TaN, the lowest volume ratio (ie., volume:volume:volume)of HF:H2O2:DIW that can be practically used is 1:1:20. However, SiN, TiN, FSG, TEOS and Cu can be removed with a minimum volume ratio of 1:1:30 of HF:H2O2:DIW. More concentrated solutions of the HF:H2O2 solution can be used with a change in the etch rates for the above mentioned materials/metal-alloys. In all embodiments, use of a higher temperature such as 40 C. to 50 C. will increase the reaction rate of the solutions to TiN, TaN, SiN, Cu, Al while all FSG type oxides remain relatively unchanged.

While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US5523593 *Mar 25, 1993Jun 4, 1996Hitachi, Ltd.Compound semiconductor integrated circuit and optical regenerative repeater using the same
US5798540 *Apr 29, 1997Aug 25, 1998The United States Of America As Represented By The Secretary Of The NavyElectronic devices with InAlAsSb/AlSb barrier
US5896875 *Aug 30, 1996Apr 27, 1999Matsushita Electronics CorporationEquipment for cleaning, etching and drying semiconductor wafer and its using method
US6149828 *May 5, 1997Nov 21, 2000Micron Technology, Inc.Supercritical etching compositions and method of using same
US6162671 *Dec 7, 1998Dec 19, 2000Samsung Electronics, Co., Ltd.Method of forming capacitors having high dielectric constant material
US6232228 *Jun 4, 1999May 15, 2001Samsung Electronics Co., Ltd.Formation of a conductive plug and the minimizing of the step-height of an interlayer dielectric layer.
US6326317 *Sep 21, 1999Dec 4, 2001National Science CouncilMethod for fabricating metal oxide semiconductor field effect transistor (MOSFET)
JPH02186614A Title not available
JPH09153598A Title not available
JPS61269804A Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6723658 *Jul 15, 2002Apr 20, 2004Texas Instruments IncorporatedGate structure and method
US7008548 *Nov 14, 2002Mar 7, 2006Lg.Philips Lcd Co., Ltd.Etchant for etching metal wiring layers and method for forming thin film transistor by using the same
US7153782 *Jul 17, 2003Dec 26, 2006Texas Instruments IncorporatedEffective solution and process to wet-etch metal-alloy films in semiconductor processing
US8257609Dec 28, 2005Sep 4, 2012Lg Display Co., Ltd.Etchant for etching metal wiring layers and method for forming thin film transistor by using the same
US8308963Jul 20, 2010Nov 13, 2012Lg Display Co., Ltd.Etchant for etching metal wiring layers and method for forming thin film transistor by using the same
CN100489158CNov 17, 2004May 20, 2009上海华虹Nec电子有限公司Use of selective silicon nitrogen oxide etching liquid by wetting method
Classifications
U.S. Classification438/745, 438/754, 134/3, 257/E21.309
International ClassificationH01L21/461, H01L21/3213, H01L21/302, C23F1/18, C23F1/02
Cooperative ClassificationC23F1/18, H01L21/32134, C23F1/02
European ClassificationH01L21/3213C2, C23F1/18, C23F1/02
Legal Events
DateCodeEventDescription
Feb 18, 2011FPAYFee payment
Year of fee payment: 8
Feb 20, 2007FPAYFee payment
Year of fee payment: 4
Aug 16, 2000ASAssignment
Owner name: TEXAS INSTRUMENTS INCORPORATED, TEXAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:EISSA, MONA M.;REEL/FRAME:011176/0064
Effective date: 19991004